Process for the preparation of a polyolefin wax

ABSTRACT

If a catalyst consisting of an aluminoxane and a metallocene of the formula I ##STR1## in particular R 5  R 6  C (Ind) 2  or R 5  R 6  C (Ind) 2  Zr(CH 3 ) 2 , is employed for the polymerization of olefins of the formula 
     
         R.sup.9 CH═CHR.sup.10 
    
     (R 9 , R 10  =H or C 1  -C 28  alkyl), the isotacticity of the polymer wax and hence the hardness and melting point can be varied simply by changing the polymerization temperature, without the molecular weight of the polymer being noticeably changed at the same time.

This application is a divisional of application Ser. No. 08/287,101filed Aug. 8, 1994 now abandoned which is a continuation of Ser. No.07/577,899 filed Sep. 5, 1990 now abandoned.

The invention relates to a process for the preparation of a polyolefinwax, it being possible for the tacticity of the polymer chains to bemodified by the choice of polymerization temperature without theviscosity number of the polymer being changed.

The preparation of isotactic polyolefin waxes (isotacticity index 80 to85%, fusion enthalpy 63 J/g, mixtures of atactic and isotacticpolyolefin chains) by means of a supported catalyst, cocatalyst andstereoregulator at temperatures of more than 95° C. is known(DE-A-3,148,229). Large amounts of nydrogen have to be employed as amolecular weight regulator.

An MgCl₂ supported contact catalyst which leads to crystalline PP waxeshaving a narrow molecular weight distribution is furthermore also known(Japanese Patent 59/206,409). This catalyst also has the disadvantagestypical of catalyst systems which have been developed for thepreparation of high molecular weight polyolefins and thus have a lowactivity in the preparation of low molecular weight polyolefins. Anundesirable mixture of isotactic and atactic chains is furthermore alsopresent here in the wax product.

Waxy random ethylene copolymers having a 1-olefin content of 1 to 15 mol%, which are prepared using a catalyst system based on zirconiumhydride-metallocene/aluminoxane, are furthermore known (Japanese Patent62/129,303). However, such metallocenes are not suitable for producingisotactic polypropylene; their activity in the polymerization ofpropylene is moreover very low.

As a result of the low catalyst activities under the reaction conditionsrequired, relatively high chlorine contents of in some cases more than1,000 ppm are found in the polymer waxes if the catalyst residues arenot removed by an expensive specific after-treatment.

The use of metallocene/aluminoxane/hydrogen catalyst systems for thepreparation of highly isotactic 1-olefin polymer waxes has also beenproposed (German Patent 3,743,321).

It has been possible to overcome the disadvantages of the processesdescribed above using this catalyst, but the high isotacticity of theproducts has led to extremely hard waxes, which is undesirable for anumber of uses of the waxes.

Concomitant phenomena of the high isotacticity achieved by this processare melting points which are too high for many uses of the waxes.Hydrogen is furthermore used to adjust the molecular weight, and aprocess which could dispense with the use of a molecular weightregulator would lead to a significant simplification of the process.

One main possibility for reducing the hardness is subsequent admixing ofatactic poly-1-olefin wax. Apart from the uneconomically high costswhich are unacceptable on a large industrial scale, this admixing leadsto non-uniform and tacky products.

It is known from the literature that a lower molecular weight polymer isformed with metallocene/aluminoxane systems at a high polymerizationtemperature than at lower temperatures (W. Kaminsky et al., macromol.Chem., Macromol. Symp., 3 (1986) 377) and at the same time the tacticityof the polymer chains is changed here only slightly (W. Kaminsky et al.,Angew. Chem. 97 (1985) 507).

There was thus the object of discovering a process with which polyolefinwaxes of different isotacticity but comparable molecular weight andnarrow molecular weight distribution can be prepared.

It has been found that the object can be achieved if a specificallybridged metallocene is used.

The invention thus relates to a process for the preparation of apolyolefin wax by polymerization or copolymerization of an olefin of theformula R⁹ CH═CHR¹⁰, in which R⁹ and R¹⁰ are identical or different andare a hydrogen atom or an alkyl radical having 1 to 28 carbon atoms, orR⁹ and R¹⁰, together with the atoms joining them, can form a ring, at atemperature of -60 to 200° C. under a pressure of 0.5 to 100 bar, insolution, in suspension or in the gas phase, in the presence of acatalyst which consists of a metallocene and an aluminoxane of theformula II ##STR2## for the linear type, and/or of the formula III##STR3## for the cyclic type, in which, in the formulae II and III, R⁸is a C₁ -C₆ -alkyl group or a C₆ -C₁₀ -aryl group and n is an integerfrom 2 to 50, wherein the metallocene is a compound of the formula I##STR4## in which M is a metal of group IVb, Vb or VIb of the periodictable, R¹ and R² are identical or different and are a hydrogen atom, aC₁ -C₁₀ -alkyl group, a C₁ -C₁₀ -alkoxy group, a C₆ -C₁₀ -aryl group, aC₆ -C₁₀ -aryloxy group, a C₂ -C₁₀ -alkenyl group, a C₇ -C₄₀ -arylalkylgroup, a C₇ -C₄₀ -alkylaryl group, a C₈ -C₄₀ -arylalkenyl group or ahalogen atom,

R³ and R⁴ are identical or different and are a mono- or polynuclearhydrocarbon radical which can form a sandwich structure with thetransition metal,

and R⁵ and R⁶ are identical or different and are a hydrogen atom, ahalogen atom, a C₁ -C₁₀ -alkyl group, a C₁ -C₁₀ -alkoxy group, a C₆ -C₁₀-aryl group, a C₆ -C₁₀ -aryloxy group, a C₂ -C₁₀ -alkenyl group, a C₇-C₄₀ -arylalkyl group, a C₇ -C₄₀ -alkylaryl group, a C₈ -C₄₀-arylalkenyl group or a --SiR₃ ⁷, --NR₂ ⁷, --PR₂ ⁷, --P(O)R₂ ⁷,--Si(OR⁷)R₂ ⁷, --Si(OR⁷)₂ R⁷, --Si(OR⁷)₃, --AsR₂ ⁷ or --SR⁷ radical,

in which R⁷ has the meaning of R¹.

The invention furthermore relates to the polyolefin wax prepared by thisprocess.

The catalyst to be used for the process according to the inventionconsists of an aluminoxane and a metallocene of the formula I ##STR5## Mis a metal of group IVb, Vb or VIb of the periodic table, preferably Ti,Zr or Hf, particularly preferably Zr.

R¹ and R² are identical or different and are a hydrogen atom, a C₁ -C₁₀-, preferably C₁ -C₃ -alkyl group, a C₁ -C₁₀ -, preferably C₁ -C₃-alkoxy group, a C₆ -C₁₀ -, preferably C₆ -C₈ -aryl group, a C₆ -C₁₀ -,preferably C₆ -C₈ -aryloxy group, a C₂ -C₁₀ -, preferably C₂ -C₄-alkenyl group, a C₇ -C₄₀ -, preferably C₇ -C₁₀ -arylalkyl group, a C₇-C₄₀ -, preferably C₇ -C₁₂ -alkylaryl group, a C₈ -C₄₀ -, preferably C₈-C₁₂ -arylalkenyl group or a halogen atom, preferably chlorine.

R³ and R⁴ are identical or different, preferably identical, and are amono- or polynuclear hydrocarbon radical which can form a sandwichstructure with the transition metal, substituted cyclopentadienylradicals being preferred. The indenyl radical is particularly preferred.

R⁵ and R⁶ are identical or different and are a hydrogen atom, a halogenatom, a C₁ -C₁₀ -, preferably C₁ -C₃ -alkyl group, a C₁ -C₁₀ -,preferably C₁ -C₃ -alkoxy group, a C₆ -C₁₀ -, preferably C₆ -C₈ -arylgroup, a C₆ -C₁₀ -, preferably C₆ -C₈ -aryloxy group, a C₂ -C₁₀ -,preferably C₂ -C₄ -alkenyl group, a C₇ -C₄₀ -, preferably C₇ -C₁₀-arylalkyl group, a C₇ -C₄₀ -, preferably C₇ -C₁₂ -alkylaryl group, a C₈-C₄₀ -, preferably C₈ -C₁₂ -arylalkenyl group or a --SiR₃ ⁷, --NR₂ ⁷,--PR₂ ⁷, --P(O)R₂ ⁷, --Si(OR)R₂ ⁷, --Si(OR⁷)₂ R⁷, --Si(OR⁷)₃, --AsR₂ ⁷or --SR⁷ radical, in which R⁷ has the meaning given for R¹.

Alkyl and aryl groups are preferred.

Preferred metallocene compounds are R⁵ R⁶ C(bisindenyl)ZrCl₂ and R⁵ R⁶C(bisindenyl)Zr(CH₃)₂.

Ph₂ C(bisindenyl)ZrCl₂ and (CH₃)₂ C(bisindenyl)ZrCl₂ are particularlypreferred.

The metallocenes described above can be prepared in accordance with thefollowing general equation: ##STR6##

The cocatalyst is an aluminoxane of the formula II ##STR7## for thelinear type, and/or of the formula III ##STR8## for the cyclic type. Inthese formulae, R⁸ is a C₁ -C₆ -alkyl group, preferably methyl, ethyl orisobutyl, butyl or neopentyl, or a C₆ -C₁₀ -aryl group, preferablyphenyl or benzyl. Methyl is particularly preferred. n is an integer from2 to 50, preferably 5 to 40. However, the exact structure of thealuminoxane is not known.

The aluminoxane can be prepared in various ways.

One possibility is careful addition of water to a dilute solution of analuminum trialkyl by introducing the solution of the aluminum trialkyl,preferably aluminum trimethyl, and the water, each in small portions,into a relatively large amount of an inert solvent which has beeninitially introduced into the reaction vessel, and in each case awaitingthe end of the evolution of gas between the additions.

In another process, finely powdered copper sulfate pentahydrate issuspended in toluene in a glass flask and aluminum trialkyl is addedunder an inert gas at about -20° C. in an amount such that about 1 molof CuSO₄. 5H₂ O is available for each 4 Al atoms. After slow hydrolysis,alkane being split off, the reaction mixture is left at room temperaturefor 24 to 48 hours, during which it must be cooled, if appropriate, sothat the temperature does not rise above 30° C. The copper sulfate isthen filtered off from the aluminoxane dissolved in the toluene and thesolution is concentrated in vacuo. It is assumed that during thispreparation process the low molecular weight aluminoxanes undergocondensation to higher oligomers, aluminum trialkyl being split off.

Aluminoxanes are furthermore obtained if aluminum trialkyl, preferablyaluminum trimethyl, dissolved in an inert aliphatic or aromatic solvent,preferably heptane or toluene, is reacted with aluminum salts containingwater of crystallization, preferably aluminum sulfate, at a temperatureof -20 to 100° C. In this procedure, the volume ratio between thesolvent and the aluminum trialkyl used is 1:1 to 50:1-- preferably 5:1--and the reaction time, which can be monitored by the splitting off ofthe alkane, is 1 to 200 hours--preferably 10 to 40 hours.

Of the aluminum salts which contain water of crystallization, thosewhich have a high content of water of crystallization are used inparticular. The particularly preferred salt is aluminum sulfate hydrate,especially the compounds Al₂ (SO₄)₃ ·16H₂ O and Al₂ (SO₄)₃ ·18H₂ Ohaving the particularly high water of crystallization content of 16 and18 mol of H₂ O/mol of Al₂ (SO₄)₃ respectively.

Another variant for the preparation of aluminoxanes comprises dissolvingaluminum trialkyl, preferably aluminum trimethyl, in the suspendingagent initially introduced into the polymerization system, preferably inthe liquid monomer, in heptane or toluene, and then reacting thealuminum compound with water.

In addition to the processes described above for the preparation ofaluminoxanes, there are others which can be used. A varying content ofunreacted aluminum trialkyl, which is present in the free form or as anadduct, is a common feature of all aluminoxane solutions, regardless ofthe nature of their preparation. This content has an influence which hasnot yet been accurately explained on the catalytic activity and whichvaries according to the metallocene compound employed.

It is possible for the metallocene to be preactivated with analuminoxane of the formula II and/or III before being used in thepolymerization reaction. The polymerization activity is in this wayincreased significantly and the particle morphology improved.

The preactivation of the transition metal compound is carried out insolution. Preferably, in this procedure, the metallocene is dissolved ina solution of the aluminoxane in an inert hydrocarbon. A suitable inerthydrocarbon is an aliphatic or aromatic hydrocarbon. Toluene ispreferably used.

The concentration of the aluminoxane in the solution is in the rangefrom about 1% by weight up to the saturation limit, preferably 5 to 30%by weight, in each case based on the total solution. The metallocene canbe employed in the same concentration, but it is preferably employed inan amount of 10⁻⁴ --1 mol per mol of aluminoxane. The preactivation timeis 5 minutes to 60 hours, preferably 5 to 60 minutes. The preactivationis carried out at a temperature of -78° C. to 100° C., preferably 0 to70° C.

A significantly longer preactivation is possible, but normally neitherincreases the activity nor reduces the activity, although it may beentirely appropriate for storage purposes.

The polymerization is carried out in a known manner in solution, insuspension or in the gas phase, continuously or discontinuously, in oneor more stages, at a temperature of -60 to 200° C., preferably -30 to100° C., in particular 0 to 80° C.

The total pressure in the polymerization system is 0.5 to 100 bar.Polymerization in the pressure range of 5 to 60 bar, which is ofparticular industrial interest, is preferred. Monomers having a boilingpoint higher than the polymerization temperature are preferablypolymerized under normal pressure.

The metallocene compound is used in this process in a concentration,based on the transition metal, of 10⁻³ to 10⁻⁸, preferably 10⁻⁴ to 10⁻⁷mol of transition metal per dm³ of solvent or per dm³ of reactor volume.The aluminoxane is used in a concentration of 10⁻⁵ to 10⁻¹ mol,preferably 10⁻⁵ to 10⁻² mol per dm³ of solvent or per dm³ of reactorvolume. On principle, however, higher concentrations are also possible.

If the polymerization is carried out as suspension or solutionpolymerization, an inert solvent which is customary for the Ziegler lowpressure process is used. For example, the polymerization is carried outin an aliphatic or cycloaliphatic hydrocarbon; butane, pentane, hexane,heptane, isooctane, cyclohexane and methylcyclohexane may be mentionedas examples thereof.

A benzine or hydrogenated diesel oil fraction can furthermore be used.Toluene can also be used. The polymerization is preferably carried outin the liquid monomer.

Olefins of the formula R⁹ CH═CHR¹⁰, in which R⁹ and R¹⁰ are identical ordifferent and are a hydrogen atom or an alkyl radical having 1 to 28carbon atoms, it also being possible for R⁹ and R¹⁰ to form a ring withthe carbon atoms joining them, are polymerized or copolymerized.Examples of such olefins are ethylene, propylene, 1-butene, 1-hexene,4-methyl-1-pentene, 1-octene, norbornene and norbornadiene. Propylene ispreferred.

The polymerization can be of any desired duration, since the catalystsystem to be used according to the invention shows only a slight drop inthe polymerization activity as a function of time.

The process according to the invention is distinguished by the fact thatthe molecular weight of the polymers prepared is practically unchangedin the temperature range between 30 and 80° C., which is of interestindustrially, but that the isotacticity of the polymer chains can bevaried between about 98 and 50% (¹³ C-NMR data) by varying thetemperature.

The hardness and melting point can in this way be adjusted in acontrolled manner without a change in the viscosity number of thepolymer, and a tailor-made product can therefore be produced. Thepolymer powders prepared are distinguished by an excellent powdermorphology--good flow properties and high bulk density.

The use of hydrogen can furthermore be dispensed with, whichadditionally results in the possibility of functionalization of thepolyolefin waxes due to the formation of unsaturated chain ends(β-elimination mechanism). Dispensing with hydrogen means a significantsimplification of the process.

The following example s are intended to illustrate the invention. Inthese examples:

VN=viscosity number in cm³ /g

M_(w) =weight-average molecular weight in g/mol

M_(n) =number-average molecular weight in g/mol

M_(w) /M_(n) =molecular weight distribution

The molecular weights were determined by gel permeation chromatography.

¹³ C-NMR spectroscopy:

II=isotactic index

n_(iso) =average isotactic block length ##EQU1## BD=polymer bulk densityin g/dm³ MV=melt viscosity, determined by means of a rotary viscometerat 170° C.

M.P.=melting point, determined by differential scanning calorimetrymeasurement (20° C./minute heating up/cooling down rate); the heat offusion was also determined by means of differential scanningcalorimetry.

The metallocene and aluminoxane were handled under an inert gas.

EXAMPLE 1 2,2-Bis-(1-indenyl)propane

18.8 cm³ (47.0 mmol) of n-butyllithium were added at 0° C. to a solutionof 5.93 g (47.0 mmol) of indene (industrial, 91% pure) filtered over Al₂O₃. After the mixture had been stirred at room temperature for 15minutes, the solution was slowly added dropwise to a solution of 7.40 g(47.0 mmol) of 1-isopropylideneindene. After the mixture had beenstirred at room temperature for 2 hours, 50 cm³ of water were added andthe mixture was extracted with diethyl ether. The yellow organic phasewas dried over MgSO₄. The residue which remained after the solvent hadbeen stripped off was chromatographed on silica gel 60. 1.5 g (13%) ofthe product (2 isomers) could be isolated with hexane/methylene chloride(10:1).

Racemic isopropylidene-bis-(1-indenyl)-zirconiumdichloride

5.30 cm³ (13.0 mmol) of n-butyllithium (2.5 M/hexane) were added to asolution of 1.50 g (5.51 mmol) of 2,2-bis-(1-indenyl)propane in 15 cm³of diethyl ether, while cooling with water. After the mixture had beenstirred at room temperature for 2 hours, 10 cm³ of hexane were added.The colorless precipitate was filtered off over a glass frit, washedwith hexane and dried under an oil pump vacuum. 1.96 g of the dilithiumsalt, which still contained about 20% by weight of diethyl ether, wereobtained (quantitative yield). This salt was added to a suspension of1.28 g (5.51 mmol) of ZrCl₄ in 25 cm³ of methylene chloride at -78° C.The reaction mixture was slowly warmed to room temperature in the courseof about 6 hours. The orange precipitate was filtered off over a glassfrit, washed with a little methylene chloride and dried under an oilpump vacuum. 930 mg (39%) of the complex racemic ((CH₃)₂C(1-indenyl)₂)ZrCl₂ were obtained as an orange-colored crystallinepowder. Correct mass spectrum (M⁺ =432).

¹ H-NMR spectrum (CDCl₃): 6.92-7.80 (m, 8, aromatic H), 6.70 (dd, 2,β-IndH), 6.15 (d, 2, α-IndH), 2.37 (s, 6, CH₃).

EXAMPLE 2

A dry 16 dm³ reactor was flushed with nitrogen and filled with 10 dm³ ofliquid propylene. 30 cm³ of a toluene solution of methylaluminoxane(corresponding to 40 mmol of Al, average degree of oligomerization ofthe methylaluminoxane n=20) were then added and the mixture was stirredat 30° C. for 15 minutes. In parallel with this, 105 g (0.243 mmol) ofracemic isopropylidene-bis-(1-indenyl)-zirconium dichloride weredissolved in 15 cm³ of a toluene solution of methylaluminoxane (20 mmolof Al) and preactivated by being left to stand for 15 minutes. Theviolet solution was then introduced into the kettle. The polymerizationwas carried out at 30° C. for 5 hours. 3.10 kg of polypropylene wax wereobtained, corresponding to a metallocene activity of 5.9 kg of PP/g ofmetallocene×h.

VN=14.0 cm³ /g; M_(w) =15,900, M_(n) =6,500, M_(w) /M_(n) =2.4;II=95.6%, n_(iso) =36, BD=360 g/dm³ ; MV=470 mPa.s; M.P.=142° C., heatof fusion=105 J/g; ball indentation hardness=1,400 bar, drawinghardness=>1,000 bar.

EXAMPLE 3

The procedure was as in Example 1, but 78.3 mg (0.181 mmol) of themetallocene were used, the polymerization temperature was 40° C. and thepolymerization time was 3 hours.

2.32 kg of propylene wax were obtained, corresponding to a metalloceneactivity of 9.9 kg of PP/g of metallocene×h.

VN=14.7 cm³ /g; M_(w) =6,500, M_(n) =5,800, M_(w) /M_(n) =2.8; II=90.2%,n_(iso) =21; BD=382 g/dm³ ; MV=490 mPa.s; M.P.=132° C., heat offusion=80 J/g; ball indentation hardness=1,170 bar, drawinghardness=>1,000.

EXAMPLE 4

The procedure was as in Example 1, but 28.9 mg (0.067 mmol) of themetallocene were used, the polymerization temperature was 60° C. and thepolymerization time was 2 hours.

2.38 kg of polypropylene wax were obtained, corresponding to ametallocene activity of 41.2 kg of PP/g of metallocene×h.

VN=13.5 cm³ /g; M_(w) =14,150, M_(n) =5,300, M_(w) /M_(n) =2.6;II=85.8%, n_(iso) =14; BD=415 g/dm³ ; MV=390 mpa.s; M.P.=125° C., heatof fusion=72 J/g; ball indentation hardness=762 bar, drawinghardness=1,000 bar.

EXAMPLE 5

The procedure was as in Example 1, but 37.3 mg (0.086 mmol) of themetallocene were used, the polymerization temperature was 70° C. and thepolymerization time was 1 hour.

2.36 kg of polypropylene wax were obtained, corresponding to ametallocene activity of 63.3 kg of PP/g of metallocene×hour.

VN=13.6 cm³ /g; M_(w) =14,750, M_(n) =5,050, M_(w) /M_(n) =2.9;II=79.7%, n_(iso) =11.5; BD=362 g/dm³ ; MV=450 mPa.s; M.P.=124° C., heatof fusion=65 J/g; ball indentation hardness=254 bar, drawinghardness=780 bar.

EXAMPLE 6

The procedure was as in Example 1, but 15.0 mg (0.035 mol) of themetallocene were used, the polymerization temperature was 78° C. and thepolymerization time was 1 hour.

1.58 kg of polypropylene wax were obtained, corresponding to ametallocene activity of 105.3 kg of PP/g of metallocene×hour.

VN=13.5 cm³ /g; M_(w) =14,200, M_(n) =5,600, M_(w) /M_(n) =2.5;II=70.5%, n_(iso) =9; BD=380 g/dm³ ; M.P.=120° C., heat of fusion=59J/g.

We claim:
 1. A process for the preparation of a polyolefin wax bypolymerization or copolymerization of an olefin of the formula R⁹CH═CHR¹⁰, in which R⁹ and R¹⁰ are identical or different and are ahydrogen atom or an alkyl radical having 1 to 28 carbon atoms, or R⁹ andR¹⁰, together with the atoms joining them, can form a ring, at atemperature of -60 to 200° C. under a pressure of 0.5 to 100 bar, insolution, in suspension or in the gas phase, in the presence of acatalyst which consists essentially of a metallocene and an aluminoxaneof the formula II ##STR9## for the linear type, and/or of the formulaIII ##STR10## for the cyclic type, in which, in the formulae II and III,R⁸ is a C₁ -C₆ -alkyl group or a C₆ -C₁₀ -aryl group and n is an integerfrom 2 to 50, wherein the metallocene is a compound of the formula I##STR11## in which M is a metal of group IVb of the periodic table, R¹and R² are identical and are a C₁ -C₁₀ -alkyl group, or a halogenatom,R³ and R⁴ are identical and are a mono- or polynuclear hydrocarbonradical which can form a sandwich structure with the transition metal,and R⁵ and R⁶ are identical or different and are a hydrogen atom, a C₁-C₁₀ -alkyl group, or a C₆ -C₁₀ -aryl group.
 2. Process as claimed inclaim 1, wherein propylene is polymerized.
 3. A process as claimed inclaim 1, wherein said M is Ti, Hf or Zr.
 4. A process as claimed inclaim 1, wherein said R¹ and R² are a C₁ -C₃ -alkyl group, or chlorine.5. A process as claimed in claim 1, wherein said R⁵ and R⁶ are identicalor different and are a C₁ -C₃ -alkyl group, or a C₆ -C₈ -aryl group. 6.A process as claimed in claim 1, wherein said temperature ranges from 0°C. to 80° C.
 7. The process as claimed in claim 1, wherein propyleneispolymerized; M is Ti, Hf or Zr; R¹ and R² are a C₁ -C₃ -alkyl group orchlorine; and R³ and R⁴ are identical.
 8. The process as claimed inclaim 7, wherein said R⁵ and R⁶ are identical or different and are a C₁-C₃ -alkyl group, or a C₆ -C₈ -aryl group.
 9. The process as claimed inclaim 8, wherein the temperature range is from 0° C. to 80° C.
 10. Theprocess as claimed in claim 9, wherein the metallocene compound iseither R⁵ R⁶ C(bis(indenyl))ZrCl₂ or R⁵ R⁶ C(bis(indenyl))Zr(CH₃)₂. 11.The process as claimed in claim 10, wherein the metallocene compound iseither Ph₂ C(bis(indenyl))ZrCl₂ or (CH₃)₂ C(bis(indenyl))ZrCl₂.
 12. Theprocess as claimed in claim 11, wherein the metallocene compound is(CH₃)₂ C(bis(indenyl))ZrCl₂.
 13. The process as claimed in claim 1,wherein the metallocene compound is racemicisopropylidene-bis-(1-indenyl)-zirconium dichloride.
 14. The process asclaimed in claim 1, wherein said olefin is ethylene or propylene. 15.The process as claimed in claim 1, wherein R³ and R⁴ are an indenylradical.
 16. The process as claimed in claim 1, wherein R⁵ and R⁶ areidentical or different and are a C₁ -C₁₀ -alkyl group or a C₆ -C₁₀ -arylgroup and said temperature is from 30° C. to 80° C.
 17. The process asclaimed in claim 15, whereinM is Hf or Zr; R¹ and R² are identical andare a C₁ -C₃ -alkyl group or a chlorine atom.
 18. The process as claimedin claim 17, wherein propylene is polymerized and said temperatureranges from 30° C. to 80° C., and M is Zr and said process takes placewithout the use or addition of hydrogen gas.
 19. The process as claimedin claim 1, wherein the metallocene compound is R⁵ R⁶ C(bis(indenyl))ZrR¹ R² wherein R¹ and R² are identical and are halogen or C₁ -C₁₀ alkylgroup and R⁵ and R⁶ are identical or different and are a C₁ -C₃ alkylgroup or C₆ -C₈ aryl group.
 20. The process as claimed in claim 19,wherein R¹ and R² are identical and are a C₁ -C₃ -alkyl group orchlorine atom and R⁵ and R⁶ are identical or different and are ahydrogen atom, a C₁ -C₃ -alkyl group or a C₆ -C₈ -aryl group.
 21. Theprocess as claimed in claim 20, wherein propylene is polymerized andsaid temperature is from 30° C. to 80° C.
 22. A process for thepreparation of a polyolefin wax by polymerization or copolymerization ofan olefin of the formula R⁹ CH═CHR¹⁰, in which R⁹ and R¹⁰ are identicalor different and are a hydrogen atom or an alkyl radical having 1 to 28carbon atoms, or R⁹ and R¹⁰, together with the atoms joining them, canform a ring, at a temperature of -60 to 200° C. under a pressure of 0.5to 100 bar, in solution, in suspension or in the gas phase, in thepresence of a catalyst which consists essentially of a metallocene andan aluminoxane of the formula II ##STR12## for the linear type, and/orof the formula III ##STR13## for the cyclic type, in which, in theformulae II and III, R⁸ is a C₁ -C₆ -alkyl group or a C₆ -C₁₀ -arylgroup and n is an integer from 2 to 50, wherein the metallocene is acompound of the formula I ##STR14## in which M is a metal of group IVbof the periodic table, R¹ and R² are identical and are a C₁ -C₁₀ -alkylgroup or a halogen atom,R³ and R⁴ are different and R³ is an indenylradical and R⁴ is a mono- or polynuclear hydrocarbon radical which canform a sandwich structure with the transition metal, and R⁵ and R⁶ areidentical or different and are a hydrogen atom, a C₁ -C₁₀ -alkyl group,or a C₆ -C₁₀ -aryl group.
 23. The process as claimed in claim 22,wherein M is Hf or Zr; R¹ and R² are a C₁ -C₃ -alkyl group or a chlorineatom, R⁴ is cyclopentadienyl and R⁵ and R⁶ are identical or differentand are a hydrogen atom, a C₁ -C₃ -alkyl group, or a C₆ -C₈ -aryl groupand said temperature is from 30° C. to 80° C.
 24. The process as claimedin claim 23, wherein the polymer produced has a viscosity number beingconstant throughout the polymerization temperature range and saidprocess takes place without the use or addition of hydrogen gas and saidtemperature is from 30° C. to 80° C.
 25. A process for the preparationof a polyolefin wax by polymerization or copolymerization of an olefinof the formula R⁹ CH═CHR¹⁰, in which R⁹ and R¹⁰ are identical ordifferent and are a hydrogen atom or an alkyl radical having 1 to 28carbon atoms, or R⁹ and R¹⁰, together with the atoms joining them, canform a ring, at a temperature of -60 to 200° C. under a pressure of 0.5to 100 bar, in solution, in suspension or in the gas phase, in thepresence of a catalyst which consists essentially of a metallocene andan aluminoxane of the formula II ##STR15## for the linear type, and/orof the formula III ##STR16## for the cyclic type, in which, in theformulae II and III, R⁸ is a C₁ -C₆ -alkyl group or a C₆ -C₁₀ -arylgroup and n is an integer from 2 to 50, wherein the metallocene is acompound of the formula I ##STR17## in which M is a metal of group IVbof the periodic table, R¹ and R² are identical and are a C₁ -C₁₀ -alkylgroup, or a halogen atom,R³ and R⁴ are indenyl radical and R⁵ and R⁶ areidentical or different and are a hydrogen atom, a C₁ -C₁₀ -alkyl groupor a C₆ -C₁₀ -aryl group and said process takes place without the use oraddition of hydrogen gas.